#include <stdio.h>
#define LETTER 'a'
int main(void)
{
	float i, j;
	char letter;

	do
	{
		printf("Please input two differences float number:\n");
		scanf_s("%f", &i);
		scanf_s("%f\n", &j);
		float g;
		g = (i - j) / (i * j);
		printf("%.2F\n", g);
	} while (i&&j != LETTER);
	printf("Thank you\n");
	return 0;
}